Santorio Santorio created the first thermometer. He was the first inventor to include a numerical scale on a device that measured changes in degrees of hotness or coolness. The thermometer he invented was the first designed to take a person's temperature.
Earlier versions of the thermometer were called thermoscopes. They could indicate whether there was a change in temperature, but they could not measure the degree to which the temperature had changed.
Daniel Fahrenheit is credited with inventing the first modern thermometer. He invented an alcohol thermometer in 1709, and he invented the mercury thermometer in 1914. He also developed the first widely accepted scale used to measure temperature.